fitting image with PSF

From: David Hui (cyhui@graduate.hku.hk)
Date: Wed Nov 10 2004 - 13:30:56 EST


Dear all,

  I am working on fitting an image from CHANDRA with a source model (del2d[d2]+const2d[c2]) and a PSF as a convolution kernel. My aim is to estimate the accurate location of a source in the image. I do the fit with SHERPA. When I want to estimate the 1 sigma error bounds for xpos and ypos of d2 by using projection. I get the following warning:

WARNING: lower uncertainty bound not found for d2.xpos
WARNING: hit parameter space hard maximum for d2.xpos
WARNING: lower uncertainty bound not found for d2.ypos
WARNING: hit parameter space hard maximum for d2.ypos

Does anybody have suggestion for the problem?

Also, I try to produce the radial profile and the fitted model with the function plot_rprof() which is a part of sherpa_plotns.sl script. But the plot doesn't with error bar.

Does anyone know how to include the error bar in the radial profile plot as well as the residual?

Thanks a lot
Best wishes
David Hui



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